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TSL2550 Datasheet(PDF) 9 Page - ams AG

Part No. TSL2550
Description  AMBIENT LIGHT SENSOR WITH SMBus INTERFACE
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Maker  AMSCO [ams AG]
Homepage  http://www.ams.com
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TSL2550 Datasheet(HTML) 9 Page - ams AG

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TSL2550
AMBIENT LIGHT SENSOR
WITH SMBus INTERFACE
TAOS029L − OCTOBER 2007
8
r
r
Copyright E 2007, TAOS Inc.
The LUMENOLOGY r Company
www.taosinc.com
Command Register
The command register is used primarily to:
D Select which ADC register will be read during a read cycle
D Switch the dynamic range of the device between standard and extended range modes
D Power the device up for operation or power it down for minimum power consumption
Table 1 shows the six primary commands used to control the TSL2550.
Table 1. Command Summary
COMMAND
FUNCTION
0x00h
Power-down state
0x03h
Power-up state/Read command register
0x1Dh
Write command to assert extended range mode
0x18h
Write command to reset or return to standard range mode
0x43h
Read ADC channel 0
0x83h
Read ADC channel 1
The content of the command register defaults to 0x00h when power is applied to the device, placing the device
into the power-down mode.
Once the TSL2550 is set to the standard range mode (0x18h) or the extended range mode (0x1Dh), the device
remains in that mode until it is powered down or the mode is changed via the command register.
The 0x03h command has two purposes: It is used to power up the device and can also be used to check that
the device is communicating properly. The value returned during a read cycle should be 0x03h.
ADC Register
The TSL2550 contains two ADC registers (channel 0 and channel 1). Each ADC register contains two
component fields that are used to determine the logarithmic ADC count value: CHORD bits and STEP bits. The
CHORD bits correspond to the most significant portion of the ADC value and specifies a segment of the
piece-wise linear approximation. The STEP bits correspond to the least significant portion of the ADC count
value and specifies a linear value within a segment. CHORD and STEP bits all equal to 0 corresponds to a
condition in which the light level is below the detection limit of the sensor. CHORD and STEP bits all equal to
1 corresponds to an overflow condition.
Each of the two ADC value registers contain seven data bits and a valid bit as described in Table 2.
Table 2. ADC Register Data Format
VALID
CHORD BITS
STEP BITS
B7
B6
B5
B4
B3
B2
B1
B0
VALID
C2
C1
C0
S3
S2
S1
S0
FIELD
BITS
DESCRIPTION
VALID
7
ADC channel data is valid. One indicates that the ADC has written data into the
channel data register, since ADCEN was asserted in the COMMAND register.
CHORD
6 to 4
CHORD number.
STEP
3 to 0
STEP number.


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